This invention relates to a medical device delivery system. The medical device delivery system has a host of uses including as a stent delivery catheter system, such as the kind used in percutaneous transluminal angioplasty (PTA) or percutaneous transluminal coronary angioplasty (PTCA) procedures. The delivery system employs a retractable sheath which exposes a medical device for deployment.
In typical PTA or PTCA procedures, a guiding catheter is percutaneously introduced into the cardiovascular system of a patient and advanced through the aorta until the distal end is in the desired artery or vessel. Using fluoroscopy, a guide wire is then advanced through the guiding catheter and across the site to be treated in the coronary artery. A balloon catheter is advanced over the guide wire to the treatment site. The balloon is then expanded to reopen the artery. The catheter may have a guide wire lumen which is as long as the catheter (over the wire) or it may be a rapid exchange catheter wherein the guide wire lumen is substantially shorter than the catheter. Alternatively, a fixed wire balloon may be used. This device features a guide wire which is affixed to the catheter and cannot be removed.
To help prevent arterial closure, repair dissection, or prevent restenosis, a physician can implant an intravascular prosthesis, or a stent, for maintaining vascular patency inside an artery or other vessel at the lesion.
Stents are also used for a variety of other purposes including maintaining the patency of any physiological conduit including but not limited to arteries, veins, vessels, the biliary tree, the urinary tract, the alimentary tract, the tracheobronchial tree, the genitourinary system, and the cerebral aqueduct.
For the purposes of this disclosure stents and medical devices may be considered to include any stent, covered stent or prosthesis or any medical device system, grafts or biologic device.
The stent may either be self-expanding or balloon expandable. For the latter type, the stent is often delivered on a balloon and the balloon is used to expand the stent. The self-expanding stents may be made of shape memory materials such as nitinol or constructed of regular metals but of a design which exhibits self expansion characteristics.
In certain known stent delivery catheters, a stent and an optional balloon are positioned at the distal end of the catheter, around a core lumen. The stent and balloon are held down and covered by a sheath or sleeve. When the distal portion is in its desired location of the targeted vessel the sheath or sleeve is retracted in a proximal direction on the catheter to expose the stent. After the sheath is removed, the stent is free to self-expand or be expanded with a balloon.
In a stent deployment system which utilizes a retractable sheath, retraction of the sheath may result in inaccurate placement of the stent for a variety of reasons including, but not limited to, the interaction of the sheath and guide catheter upon retraction. One way of dealing with this is to make the retractable sheath long enough so that it will be contained in the guide catheter at all times. This increases system profile, reduces flexibility and creates excess friction upon sheath retraction.
Another way of dealing with this issues is described in commonly assigned U.S. Pat. No. 5,772,669. The stent delivery system disclosed therein comprises, in a catheter having a proximal outer shaft, a retractable distal sheath concentrically arranged around a stent receiving portion of the catheter and a pull back means operatively connected to the distal sheath. The catheter is further arranged so that the retractable sheath or a member connected thereto is pulled into the proximal outer shaft of the catheter during retraction of the distal sheath thereby freeing the loaded stent.
All U.S. patents and applications all other published documents mentioned anywhere in this application are incorporated herein by reference in their entirety.
Without limiting the scope of the invention in any way, the invention is briefly summarized in some of its aspects below.
In one embodiment, the invention is directed to a medical device or stent delivery system comprising an inner tube having a proximal region and a distal region and a medical device or stent receiving region at the distal end of the inner tube for receiving a medical device or stent thereabout. The system further comprises a medical device or stent sheath disposed about the medical device or stent receiving region. The medical device or stent sheath is movable relative to the inner tube. A medical device or stent sheath retraction device extends proximally from the medical device or stent sheath. An outer sheath is disposed about the inner tube. The outer sheath has a proximal and a distal end, and is disposed about a portion of the medical device or stent sheath retraction device. The distal end of the outer sheath terminates proximal of the medical device or stent receiving region. The medical device or stent sheath is movable relative to the outer sheath.
In another embodiment, the invention provides a stent delivery system which comprises an inner tube with a stent disposed about a portion of the distal region of the inner tube and a stent sheath disposed about the stent. The stent sheath is movable relative to the inner tube. A stent sheath retraction device extends proximally from the stent sheath. An outer sheath is disposed about a portion of the stent sheath retraction device. The outer sheath is characterized by a length which does not exceed the difference in length between the inner tube and twice the length of the stent. The outer sheath is located proximal to the stent sheath. The stent sheath is movable relative to the outer sheath.
In yet another embodiment, the invention provides a stent delivery system which comprises an inner tube with a stent disposed about a portion of the distal region of the inner tube, a stent sheath disposed about the stent, a stent sheath retraction device extending proximally from the stent sheath and an outer sheath disposed about a portion of the stent sheath retraction device. The outer sheath is characterized by a length which does not exceed the difference between the length of the inner tube and the length of the stent. The outer sheath is located proximal to the stent sheath. The stent sheath is movable relative to the outer sheath and to the inner tube.
In yet another embodiment, the invention provides for a stent delivery system which comprises an inner tube with a stent disposed about a portion of the distal region of the inner tube, a stent sheath disposed about the stent, a stent sheath retraction device extending proximally from the stent sheath and an outer sheath disposed about a portion of the stent sheath retraction device. The outer sheath terminates at least one stent length proximal of the stent. The stent sheath is movable relative to the outer sheath and the inner tube.
Additional details and/or embodiments of the invention are discussed below.